海洋环境下因氯离子侵蚀而导致的混凝土结构表观劣化问题，是海洋土木工程结构设计建设需要面临的主要挑战之一。如何对海洋环境下的混凝土结构进行耐久性设计和性能控制，是此类工程项目的设计部门和建造单位需要解决的重要问题。耐久性可靠度定量设计方法是解决该问题的科学手段，已被用于港珠澳大桥工程的结构耐久性设计，并首次写入了《混凝土结构耐久性设计标准》（GB/T 50476-2019）。但该方法由于以钢筋脱钝为极限状态、忽略了参数的空间变异性、也缺少与之相匹配的产品质量控制理论，目前尚存在较多需要补充和完善的地方。本文旨在探讨如何在可靠度定量设计方法基础上，改进海洋氯化物环境下混凝土结构耐久性设计框架，并建立与之匹配的耐久性参数质量检验方法。主要工作总结如下：1、梳理现有与混凝土表观劣化预测计算相关的研究成果；引入随机场理论和离散化构造方法，以描述耐久性参数的空间变异性；考虑构件生产的“批次效应”，基于蒙特卡洛模拟方法建立了海洋环境下混凝土构件表观劣化二维随机模拟方法。2、对华南某近海工程沉管隧道的耐久性参数实测数据进行统计分析，验证本文提出的“批次效应”，并测算参数统计特征；以该工程为例，开展其沉管隧道表观劣化的二维随机模拟，以评价其耐久性水平。研究发现，其实体构件在设计使用年限内不会发生明显表观劣化，其耐久性水平高于设计预想水平。3、建立了构件层面耐久性设计方法的基本框架，提出在原有的耐久性定量设计方法基础上，借助于表观劣化模拟方法，实现对设计方案的迭代优化；提出了结构维护的三种临界劣化状态，并运用蒙特卡洛模拟方法比较了不同的耐久性可靠度设计水平、耐久性参数组合和维护方案情况下，结构在构件层面劣化风险、维护需求等方面的耐久性性能表现。4、针对华南某近海工程，梳理并完善了氯离子扩散系数质量检验方案，提出了制定类似工程质检方案的通用方法；借助于蒙特卡洛模拟，探讨了质量检验对改善工程耐久性能的意义及施工方和业主方所承担的风险水平；建立了考虑保护层实测值的双参数耐久性质量检验方法。
Surface deterioration due to chloride ingress is one of the major challenges in design and construction of reinforced concrete (RC) structures in marine environment. How to conduct the durability design and performance control of major marine concrete structures is one of the main issues that both designing and construction parts need to deal with. The reliability-based and quantitative design approach is a scientific mean to solve the problem and had been implemented in the durability design of the Hong Kong-Zhuhai-Macao Sea-link Project. The approach was firstly mentioned in the amendment of Code for Durability Design of Concrete Structures (GB/T 50476-2019) in 2019. However, it needs to be supplemented and improved in several aspects, including considering only the limit state of depassivation of steel reinforcements, ignoring the spatial variability of durability parameters and lacking the corresponding theory of conformity control for productions.The dissertation aims at developing a durability design framework for marine concrete structures under chloride attack, and proposing the corresponding conformity control method for durability parameters, on the basis of the existing reliability-based durability quantitative design approach. The main works are as follows:1. The existing findings in prediction and calculation of concrete structures’ surface deteriorations were summarized. To characterize the spatial variability of durability parameters, the random field theory as well as its discretization and constructing method were induced. The “batch effect” in members’ production was considered. The 2-dimensional random simulation approach for surface deterioration of RC members under chloride-attack in marine environment was established based on Monte Carlo Simulation method.2. Statistic analysis of in-situ data for durability parameters of an immersed tube tunnel in an offshore construction project in south China was performed. The “batch effect” proposed by this dissertation was proved, and the statistic characteristics of durability parameters were calculated. 2-dimensional simulation for surface deterioration of immersed tube tunnel in this project was conducted, and durability performance of the project was examined. It’s found that obvious surface deterioration will not occur during the design service life of 120 years, and the actual durability performance is much better than the design expectation.3. The basic framework of durability design approach on member level was established, by performing the surface deterioration simulation and then the iterative optimization of the scheme, on the basis of the existing durability quantitative design approach. Three critical deterioration states for structural maintenance during service life were proposed. The durability performances including deterioration risks, maintenance demands, etc. were compared under various durability design levels, combinations of durability parameters and maintenance plans.4. The conformity control scheme for chloride diffusion coefficient of the offshore construction project in south China was reviewed, amended, and improved. The general method for designing a conformity control scheme for chloride diffusion coefficients in similar engineering projects was developed. By mean of Monte Carlo Simulation method, it was found that the conformity control scheme will improve the durability performance of the production lots with different efficiency, depending on the construction qualities of the lots. The bivariate conformity control scheme for chloride diffusion coefficient was established to consider the actual concrete cover depths.
